beater bike for rain and store runs, converting an old 12 speed and adding fenders and racks/panniers

110 bcd crank with 52t and 40t rings

should i:

40/15 to keep it mostly the same as my good bike (70 gi)
40/16 for slightly easier ride with groceries and panniers and whatnot (65 gi)
52/20 for an inbetween of those 2 (68 gi)

granted im not trying to put this thing in a race, but with a huge ring on a tiny spider i know the 52 will be more flexy

really im just thinking out loud here, would a 3-6 gi change even be noticeable? (from my daily rider of 71 gi)